High-frequency multiplex signaling system



Oct. 6, 1925- 1.. ESPENSQHIED HIGH FREQUENCY MULTIPLEX SIGNALING SYSTEM Filed April 9," 1921 gvweutoz reamed 011.6, 1925.

UNITED STA LLOYD EsrENsc IEn, E oUE Ns, NEW YORK, AssIGNoE '10 AMERICAN .rELErHoNE AND TELEGRAPH COMPANY, A CORPORATION or NEW YORK.

HIGH-FREQUENCY MULTIPLEX STGNALING SYSTEM.

Application filed April 9, 1921, serial No. 459,834. I

To all whom it -mag concern:

Be it known that I, LLoYn ESPENSCHIED, residing at Queen's, in the county of Queens and State of New York, have invented cert'ain Improvements in 'High-Frequency Multiplex Signaling Systems, of which the following is a specification. v This invention relates to multiplex signaling system and more particularly to a terminal circuit arrangement embodying the use of amplifiers adapted to amplifythe'side band and the carrier frequency oscillations received by the said terminal circuit.

This application is a continuation in part of my copending application, Serial No. 327,501 filed September 30, 1919, entitled 'High frequency multiple-x signaling system. I

The broad object of the invention is to improve the transmission efficiency and the transmission quality of carrier current circuits. One feature is the provision of a carrier current amplifier for improving the I transmission. efficiency of the carrier circuit. 5 A furthei object'off the invention isto provide -ineans-whereby the ratio of the unmodulated carrier current. transmitted over thesystem to the modulated or. side band component may becontrolled for the "pur- 0 poseofinsuring good qualityin thecarrier' transmissioncircuit, 1 'A comprehensive understanding of the invention will be facilitated by recognizing that in the ordinary form of carrier current transmission represented by radio, there are involved re'ally'. two-channels, one the unmodulated'carriercurrent which is transmitted over the'syst'em at the original car rier frequency, and the other I the modulated or side 'band'eompone'nt which is transmitted atafrequency difiering from. the original carrier frequency by an amount corresponding to the signaling frequency. .Th'eset-wo channels are commonly treated in radio, for example, as a single channel, and at the receiving end are fed unseparated into the detector; The detecting action obtains, however, only h virtue of modulation between, that is, the eating together of, the currents of the two channels, the carrier and one.or both side bands. The present invention is concerned with that type ofcarrier current system, either wire or Wireless, wherein the carrier is transmitted with the side bands as high frequency in ordinary radio practice, as distinguished from the type ployed for multiplex service over wires wherein the carrier frequency was sup sending end and resupplied pressed at the at the receivingend by a control system.

One feature of the invention resides in the use of an amplifier inthe high frequency part of the circuit which amplifies simultaneously both the carrier and the side band currents. A given amplification inserted in this manner in the high frequency circuit results in a twofold amplificationof the detected current by virtue of the fact that the I amplitude of the detected current is a function of the product of the amplitudes of the carrier and the side band currents.

This invention will be better understood .from the following description when read in connection with the attached drawing,-

of which Figure 1 shows an arrangement for amplifying to the same degree both the earrier frequency and the side band frequency oscillations, Figure 2 shows an arrangement us ng a common translating circuit adapted to amplify the low frequency signals and Ithe side band oscillations'before impressing them u on amodulating and demodulating device aving a local ,sourceef carrier 6s-' fcillations.associated therewith, ,and Fig. 3

,showsan arrangement having separate translating circuits individual to the tran'sy ,:\,I nitt'iii'g and receiving paths respectively 7 whereby the processes of amplifying, mod'uilating and demodulating are carried out, Thecircuit arrangemenbshown in Figure 1 discloses a means whereby the received oscillations of carrier frequency and the .modulated oscillations, that is the, side band component,f the frequency of which differs from the, original carrier frequency by an amountcbiresponding to the signal fresimultaneously and qliliency mafy be lified t e ampli ed osci lations impressed upon a detectingdevice. In the figure, X represents an antenna which is tu'ne d for the reception of oscillations of carrier frequency,

- and ailsofor oscillations of frequencies represented by the side band. The antenna X is connected with the input side of the amplifying circuit by means ofa transformer T, which preferably is ofthe tight-coupling" step-up adapted torela type. Thistransformer is te more efficiently the low re- '55 ofcarrier system first emsistance antenna circuit with the high resistance of the gap between the grid and the filament. adapted to amplify the impressed oscillag tions is shown. n the figureas; being of the The amplifier A which is well known vacuumtt-ube type,f but it is to be understood that any type of non-distortmg amplifier may used instead. The transformer T which is a tight-coupling step-down tr'ansformer, is adapted to-asso- 'ciate the high resistance out ut circuit of 1 the amplifier A with the high; frequency tuning circuit '1. The transformer T is of i the loose-coupling type for impressing the oscillations of the tuning circuit 1 upon the closed tuning circuit 2 in the input side of the detector D in the output side of which is the receiver R. In the operation of this circuit the oscillations of the frequencies received by the antenna X are impressed by the transformer T upon the input side of the circuit containing the amplifier A Theamplifier A is adapted to amplify the carrier frequency and also; the frequencies represented by the side band component. These frequencies are impressed upon the circuit 1 and in turn upon the input side of the detector D The amplification of the carrier frequency, together with the frequencies of the side band results-ina twofold amplification of the detected current in the outputside of the device D by'virtue of the fact that the amplitude of the detected current is a function of the product of the amplitudesof the carrier and the side band currents.

'wire circuit is a translatin In Figure 2, L shows a source of low frequency signaling currents which is connected with the terminal circuit by means of a transformer T having a network N associated therewith'adapted to balance the line 11 jlhis term'inal circuit, which is of the.Tfou ii iiviretype,- has associated with it low frequency filters F and F and the high frequency filters F and F The transmitting path of this circuit is connected with the branch transmission circuit ,TL, which is in turn connected with themain transmissionline MLjhy means of transformer T A network N associated with transformer T is-adapted to balance the line ML. An-

other circuit I423 is connected with the main transmission line ML'through the low frequency filter'F the function of the said line being to transmit lowfrequency voice currents over the line ML-simultaneously with the transmission of the high frequency signaling currents from the terminal circuits.

High frequency oscillations received over the line ML pass through the high frequenc filter {F and are impressed on the branc receiving circuit RL by the transformer T Connected between the two sides of the four circuit which forms-a common path for t e outgoing and incoming currents of the terminal "circuit.

The input side of this translating circuit is connected with one side of the terminal circuit by means of the transformer T which is of a type designed for the efficient transfer of both low frequency and high frequency currents from the terminal circuit to the translating circuit. Connected with the "translating circuit is an amplifier A adaptcuit L are impressed by the transformer T upon the low frequency circuit 1 and passing 5 through the filter F are impressed upon the translating, circuit by the transformer T These low frequency currents are amplified by the amplifier A and by'means of the device MD serve to modulate the carrier current. The modulated high frequency oscillations are impressed upon the high freque icy output circuit from whence they pass through the high fre uency filter F 4 to the transmission lines T and ML. Simultaneously with the transmission of the modulated high frequency oscillations unmodu lated carrier oscillations produced -b the "source Gr are transmitted V through" evice MD and over the lines TL and v ML to the corresponding terminal circuit at the opposite end of the said line.

The modulated high frequency oscillations received from the terminal circuit at the said other end of the line ML are impressed upon the branch receiving line BL and pass through the filter F into the translating circuit. Simultaneously with the reception of these modulated oscillations unmodulated oscillations of the same frequency are received by the line RL and are impressed upon the translating circuit passing through the filter F which is adapted to transmit the carrier frequency and the band of frequencies based thereon. The received band of oscillations and the carrier oscillations are amplified together by the amplifier A .and are impressed by means, of the transformer T uponthe device MD in which they are modulated. The low frequency signaling current resulting therefrom passes through the filter F to the line L and actuates the low frequency signaling apparatus associated therewith. The amplification of the oscillations of the side band frequencies and of the carrier frequency itself results in a two-fold amplification of the detected current by virtue of the fact that the amplitude of detected current is a function of the product ofthe amplitude of-the carrier oscillations and the amplitude of the side band oscillations. Thus an amplification which doubles the received high frequency currents of both the side band and of the carrier sup ply results in quadrupling the detected current as a result of this product relationship. It is therefore apparent that the arrangement) shown in Figure 2 results in a substan tial gain in the transmission of signals by a system employing high frequency carrier "currents. As has been stated, the modulated high frequency oscillations transmitted over the lines TL and Mill from. the terminal circuit shown in Figure 2 will be received ina circuit of any type such as the 22 type "circuit wherein separate 1 *high frequency K form thesame function as in Fig. '2. frequency variations fromf'the line. L will low-passfilter F will amplifiers are emploged for sendingandreceivingal Such modi cation is shown in *Fig. 3 in whichthe same reference characters have been used to represent parts which er:

be. impressediby the line transformer upon the circuit land after pissing through. the

'. amplified to the desired degree by the amplifier A and then will be impressed upon'themodulato'r M which has a source -of unmo'dulate'd. high frequency" oscillations connected therewith.

.The'r'esultant modulated oscillations will be transmitted throughthe high-pass filter F 4 to the line TL, from which they will be transmitted to the 'main transmission line ML in the same manner as described in connection with Fig. 2; .The modulated high; frequency oscillations and unmodulatedlic'arrier oscillations which aretransmitted from: the distant end of the line ML will be impressed upon the receiving line. BL and will pass through the high-pass filter F assuming that the frequencies are within the rangeof transmission of this filter. These oscillations will be amplified by the amplifier A andthe resultant amplified oscillations willbe impressed upon the demodulating "device D wherein the signal com onent will be detected and will be transmitted through the -p filter a to e l n ali s-trans vance their respective line circuits lating-circuits in the transmitting, and receiving paths of. Fig. 3, re resented by the rectangles designated "amp ifier, modulator for demodulator, shouldpreferably be of the -form represented inFig. 2 within the dotted rectangle. y I

It will be 'seen that this invention pro-. vides means whereby the received carrier frequency and also. the freqpencies repre- .sented by the received side and or bands may beam lified simultaneously.- It is also.

apparentt at the arrangement shown ,v in Figure 2 is adapted to amplify simultane ously received oscillations of thecarrier frequency and also the low frequency signals originating upon the line L which pass through the filter F, and are impressed uponthe translating circuit by the transformer T Since the. filters F and F 2 are adapted to transmit the same band of low frequency currents,and .F and F are adapted to transmit the same band of high frequency currents, singing around the circuit over either the low frequency path or the high frequency path is prevented by the use of the conjugate transformers T and T and the networks N and N ;adapted to bail- 1 and ML.

Although Figure .1 shows the invention 9 embodied in a radioicircuit and Figure 2 shows it n a wire signaling circuit it is to be understoodthat the invention is not limited to such specific forms but that-p it is capable of embodiment in other a'nd'different forms without departing from'the spirit and scope of the app endedclaims.

What is claimed is: I r c 1. In a signaling system' adapted for the ,transmission"andfreception of high frequency signals and characterized by a translating circuit common to the transmitting and receiving paths of thesaid system, the

method which eonsists in simultaneously amplifying in 'a common. circuit low frequency signals and m0dulated higl1" frequency signals, modulating an unmodulated high frequency carrier current in accordance with the said low frequency signals, demodulating the] modulated high frequency oscillations by means of'the said carrier current, and vtransmitting the currents resulting from such modulation and de-a modulation.

2. In a signaling system, thecombination with a low frequency signaling circuit of a high frequency transmission circuit,a connecting circuit providing paths for. the oppositely traveling currents from the said signaling circuit and the said transmission circuit, the said connecting circuit having a translating circuit common tofthe saidpaths, the said translating circuit having means for amplifying thecurrcnts impressed upon the said connectingcircuit by the said low frequency and the said high frequency circuit,- and means for modulating and demodula'ting the said amplified currents.

' 3". Ina signaling system, the combination with allow frequency signaling circuit of a high frequency transmission circuit, a fourwire connecting circuit between the said low frequency circuit and said high frequency circuit having frequencyselecting means in each of the two-wire branches to proyid e paths for the oppositely traveling currents, and a translating circuitcommon to the said paths of thesaidlconnecting circuit, the said translating circuit having means to'amplify the transmitted and received currents impressed uponsaid translating circuit.

4. In a signaling system, the combination with a loW frequency signaling circuitof a-- high frequency transmission circuit, a four- Wire connecting circuit between the said loW frequency circuit and the said high frequency circuit, providing two-wire paths for the oppositely traveling currents, each pat-h having associatedtherewith a low-pass filter and a band filter, and a translating circuit common to both of said paths containing means to amplify the currents impressed on the said translating circuit, and means to modulate and demodulate' the said amplified currents. v

5. In a signaling system, the combination with a low frequency signaling circuit, of

a high frequency transmissioncircuit, and

a four-wire connecting circuit characterized by filters in the two-wire branches to establish definite paths for the transmitted and received currents and also characterized by means to amplify transmitted and received currents before modulationor demodulation.

6. In a signaling system, the combination with a low frequency circuit, of a high frequency circuit, a four-wire connectingcircuit comprising two two-wire branches each having a low pass filter and a band filter therein and a translating circuit bridged across said branches and comprising an aim pufier, a modulating and demodulating device whereby currents from the said low frequency circuit and from the said high fre quency circuit may be amplified before modulation or demodulation and means for impressing upon the translating circuit the low frequency andhigh frequency currentsfrom one of said two-wire branches. v

7. Ina signaling system the combination with two lineoircuits, of networks 'to balance the. said line circuits, afour-wira'connecting circuit interposed between the said line circuits and electrically related thereto April 1921. i

. LLOYD ESIENSCHIED. 

